Green’s Dictionary of Slang

slamming and jamming n.

(US black) of a disc jockey, playing exciting music.

[US]Eble Campus Sl. Nov. 7: slammin’ jammin’ throw down happy feet – expression of sheer joy.
[US]‘Master Pimp’ Pimp’s Rap 1: The Dj was slamming and jamming with that rap music.